1. Field of the Invention
This invention relates to polymers containing an inorganic backbone structure including sulfur atoms. More particularly, this invention relates to homopolymers and copolymers containing alternating sulfur (VI) and nitrogen atoms as the repeating units and a method for preparing these polymers.
This invention also relates to a method for preparing these polymers using 1) compounds of hexavalent sulfur, specifically the corresponding N-triorganosilylsulfonamide or N,N-bis(triorganosilyl)sulfonamide, 2) a dichloro- or dibromotriorganophosphorane and 3) a phenol or fluorinated alcohol as reactants.
2. Description of the Prior Art
The polymers referred to in this specification as polyorganooxothiazenes contain repeating units of the general formula ##STR1##
Polyoxothiazenes containing a fluorine atom or an amino group as the substituent represented by Y in formula 1 are reported in U.S. Pat. No. 3,017,420, which issued to Cramer on Jan. 16, 1962. A disadvantage of these polymers is their poor hydrolytic stability and their susceptibility to degradation in the presence of nucleophilic reactants. In addition, the susceptibility to thermally induced degradation of these polymers would be expected to be inferior to that of polymers containing a hydrocarbon radical as the substituent represented by Y.
The preparation of oxothiazene telomers that could contain up to ten repeating units per molecule and trifluoromethyl as the substituent represented by Y in formula 1 is reported by Bechtold et al in the Journal of Fluorine Chemistry [Vol. 19, page 379 (1982)]. The telomers were prepared from the sulfinyl azide CF.sub.3 S(O)N.sub.3, a compound of tetravalent sulfur. Because of their tendency to decompose azido compounds as a class are difficult to synthesize, store and manipulate.
An article by Levchenko et al. [Zh. Obsch. Khim. 32, 2585 (1962) reports a polyorganooxothiazene containing a phenyl radical as the substituent represented by Y in formula 1. This polymer is characterized only by a softening temperature of from 80.degree. to 100.degree. C. The polymer is prepared by heating the phenyl ester of areneiminosulfonic acids of the general formula ArS(O)(.dbd.NH)OC.sub.6 H.sub.5 where Ar represents a phenyl radical.
Carl Johnson in the Journal of Organic Chemistry, 44, 13 (2055-2061), published on Jun. 22, 1979, reports obtaining a polymer from the reaction of a sulfonimidoyl chloride corresponding to the formula PhSX(O).dbd.NH, where Ph represents a phenyl radical and X is chlorine with pyridine, methylamine or dimethylamine. The hydrocarbon radical represented by R is aryl. The article does not describe the isolation of the polymers nor does it provide any structural or other characterization data for these polymers.
The polyorganooxothiazenes reported by Bechtold, Levchenko et al. and Johnson were prepared using compounds of tetravalent sulfur as starting materials. These starting materials suffer from one or more of the following disadvantages: difficult to synthesize and/or purify, not readily accessible or available, malodorous, and limited shelf life due to decomposition during long-term storage. In addition, some of the reactants used to convert the sulfur in these compounds from the tetravalent to the desired hexavalent state suffer from the same disadvantages as the compounds they are intended to convert. Moreover, some of these reactants are high energy compounds, and potentially explosive.
By contrast, the sulfonic acids and derivatives of these acids, such as the chlorides, anhydrides and sulfonamides, are generally very stable, readily available, and can be handled in large quantities without exercising more than the ordinary precautions involved in handling acidic and corrosive materials.
One objective of this invention is to provide a class of polyorganooxothiazenes wherein the hydrocarbon radical bonded to sulfur is other than the aromatic radicals disclosed in the aforementioned article by Levchenko et al.
A second objective of this invention is to provide a method for preparing high molecular weight polyorganooxothiazenes using derivatives of organic sulfonic acids as reactants. In accordance with the method discovered by the present inventors, the N-triorganosilyl organosulfonimidates that are thermally condensed to form the present polymers are, in turn, prepared by reacting an N-trimethylsilyl organosulfonamide or an N,N-bis(triorganosilyl)alkanesulfonamide of the formula EQU R.sup.1* SO.sub.2 N[Si(R.sup.2).sub.3 ].sub.p (H).sub.2-p
Where R.sup.1* represents a monovalent hydrocarbon or substituted hydrocarbon radical, R.sup.2 represents a monovalent hydrocarbon or halogenated hydrocarbon radical and p is 1 or 2, with a triorganodihalophosphorane followed by reaction of the resultant sulfonimidoyl halide, R.sup.2.sub.3 SiN.dbd.S(O)R.sup.1* X, where X represents chlorine or bromine, with a phenol or a fluorinated monohydric alcohol. This route to sulfonimidoyl halides has not been reported in the literature.